Photochromic Fentanyl Derivatives for Controlled μ-Opioid Receptor Activation

Photoswitchable ligands as biological tools provide an opportunity to explore the kinetics and dynamics of the clinically relevant μ-opioid receptor. These ligands can potentially activate or deactivate the receptor when desired by using light. Spatial and temporal control of biological activity allows for application in a diverse range of biological investigations. Photoswitchable ligands have been developed in this work, modelled on the known agonist fentanyl, with the aim of expanding the current “toolbox” of fentanyl photoswitchable ligands. In doing so, ligands have been developed that change geometry (isomerize) upon exposure to light, with varying photophysical and biochemical properties. This variation in properties could be valuable in further studying the functional significance of the μ-opioid receptor.     

Structural Switching of a Distorted Trigonal Metal-Organic Cage to a Tetragonal Cage and Singlet Oxygen Mediated Oxidations

Construction of metal–organic cages with unique architecture and guest binding abilities is highly desirable. Herein, we report the synthesis of a distorted trigonal cage ( 1 ) from a twisted tetratopic ligand ( L ) and a Pd^II acceptor. Surprisingly, 1 exhibited a complete structural reorganization of its building units in the presence of C₇₀ and C₆₀ to form guest-encapsulated tetragonal cages, (C₇₀)₂@ 2 and (C₆₀)₂@ 2 , respectively. These guest-bound cages were found to be potential ¹O₂ generators, with the former effectively catalyzing two different varieties of ¹O₂-mediated oxidation reactions.